The packaging of certain liquids requires that they be placed in a container while hot to provide for adequate sterilization. Hot-filled containers are designed for this purpose. During filling, the container is subjected to elevated temperatures on the order of 82.degree. C. (the product temperature) or higher. The container is then capped and as the product cools, a negative internal pressure is formed in the sealed container.
Biaxially-oriented polyethylene terephthalate (PET) beverage bottles have been designed to receive a hot-fill product with a minimum of thermal shrinkage and distortion. One such bottle is described in U.S. Pat. No. 4,863,046 entitled "Hot Fill Container," which issued Sep. 5, 1989 to Collette et al. The Collette et al. container has six recessed vacuum panels in the middle panel section of the container. The panels reduce the magnitude of the vacuum generated in the filled and capped container to prevent any large uncontrolled shape distortion. As the product cools, the vacuum panels (all of them) deform and move inwardly in unison. A wrap-around label covers the vacuum panels and is supported by raised central wall portions in the vacuum panels, post areas between the vacuum panels, and horizontal glue land areas above and below the vacuum panels. Longitudinal (vertical) recessed ribs may be provided in the post areas and raised wall portions in the vacuum panels to increase the longitudinal stiffness of the panel section.
The design of the vacuum panels may vary; other designs are illustrated in: 1) U.S. Design Pat. No. 315,869, "Container Body for Liquids Or The Like," Apr. 2, 1991 to Collette; 2) U.S. Pat. No. 5,255,889, "Modular Mold," Oct. 26, 1993 to Collette et al; 3) U.S. Pat. No. 5,178,289, "Panel Design For A Hot-Fillable Container," Jan. 12, 1993 to Krishnakumar et al.; and 4) U.S. Pat. No. 5,303,834, "Squeezable Container Resistant To Denting," Apr. 19, 1994 to Krishnakumar et al.
Providing a container with a gripping portion to facilitate handling has become increasingly popular in recent years. Generally, it is not sufficient to simply add a gripping portion to the container; rather, the container design and/or wall thickness needs to be modified to strengthen the container walls and control the amount of deformation which occurs when the container is grasped. Increasing the container wall thickness is undesirable as this leads to a substantial increase in the amount of material and thus cost of the container. These increased costs are unacceptable in the extremely competitive container industry. Thus, as the demand for grippable bottles has continued to grow, especially in the soft-drink and sports-drink industries, new and improved designs that retain their shape when firmly grasped are required.